Characters in the film at several points mention "the company" they work for, but which is never named. In reality, this company was the Mitsubishi Corporation, which owned Hashima Island until 2002.
On July 28, a special screen was held for UNESCO officials and diplomats in Paris at the headquarters of Metropolitan Filmexport. The aim was to raise awareness of the hidden history of the Hashima Island and how the Koreans were forced into harsh labour at an underground coal mining factory on the island during Japan's rule of Korea.
Hashima Island is currently an abandoned island. Mitsubishi closed the island's mine in 1974, and all inhabitants were evacuated.
Hashima Island is one of 505 uninhabited islands in Nagasaki Prefecture. It is located 15 kilometers (9 miles) from the city of Nagasaki.
While Hashima Island is a real place and forced labor of Korean and Chinese nationals did take place there, the characters, plot and specific events described in the film are fictional.